diff --git a/mantidimaging/gui/main_window/mw_view.py b/mantidimaging/gui/main_window/mw_view.py
index 3c65652de09..ddb847fb196 100644
--- a/mantidimaging/gui/main_window/mw_view.py
+++ b/mantidimaging/gui/main_window/mw_view.py
@@ -1,7 +1,8 @@
 from __future__ import absolute_import, division, print_function
 
+import matplotlib
+
 from logging import getLogger
-from PyQt5 import Qt, QtCore
 from PyQt5 import Qt, QtCore, QtWidgets
 
 from mantidimaging.core.algorithms import gui_compile_ui
@@ -51,7 +52,8 @@ def show_save_dialogue(self):
         self.save_dialogue.show()
 
     def stack_names(self):
-        # unpacks the tuple and only gives the correctly sorted human readable names
+        # unpacks the tuple and only gives the correctly sorted human readable
+        # names
         return self.presenter.stack_names()
 
     def stack_list(self):
@@ -84,12 +86,13 @@ def create_stack_window(self,
         return dock_widget
 
     def remove_stack(self, obj):
-        getLogger(__name__).debug("Removing stack with uuid {}".format(obj.uuid))
+        getLogger(__name__).debug("Removing stack with uuid %s", obj.uuid)
         self.presenter.remove_stack(obj.uuid)
 
     def algorithm_accepted(self, stack_uuid, algorithm_dialog):
         """
-        We forward the data onwards to the presenter and then the model, so that we can have a passive view.
+        We forward the data onwards to the presenter and then the model, so
+        that we can have a passive view.
 
         :param stack_uuid: The unique ID of the stack
 
@@ -104,3 +107,12 @@ def show_error_dialog(self, msg=""):
         :param msg: Error message string
         """
         QtWidgets.QMessageBox.critical(self, "Error", msg)
+
+    def closeEvent(self, event):
+        """
+        Close all matplotlib PyPlot windows when exiting.
+
+        :param event: Unused
+        """
+        getLogger(__name__).debug("Closing all PyPlot windows")
+        matplotlib.pyplot.close("all")